This invention relates to apparatus for obtaining three-dimensional volume data of an object, and particularly to an apparatus for obtaining three-dimensional volume data of an object by picking up the image of the object and processing the image signal.
Recently, production of images by using a computer (CG: Computer Graphics) is very popular in broadcasting and movie production. In this CG, the image of an object (for example, a person, or a building) to be displayed on a screen is produced as a two-dimensional image from the wire frame model that is produced from the volume data of the shape of the object. Since the object image is produced on the model of volume data, the three-dimensional operation such as rotation and deformation of a component is easy to make.
So far, the following methods have been used for obtaining three-dimensional volume information of an object:
(1) Slit light or laser light indicating coordinates is irradiated on the object itself, thereby obtaining three-dimensional coordinates on the object surface.
(2) Coherent light is irradiated on the object so as to produce a moire image, and the shape is obtained by measuring the distance to the object from this moire image.
(3) An approximate shape of the object of interest is generated on the display by computation, and the operator edits this shape while viewing the shape.
The techniques of methods (1) and (2) are described in detail in "Handbook of Optical Measurement" (edited by Toshiharu Denko and published by Asakura Shoten), pp 582-595.
The methods (1) and (2) need special measuring apparatus. Because it takes a long time to measure, a person and so on are compelled to stand still when their shapes are inputted. In the method (3), since the shape is modeled by use of a computer, a skilful operator must edit in a long time.
It is also well known that the image of an object is photographed without a special apparatus and used for measuring the shape, as described in the literature of "Digital Composition of Images with Increase Depth of Focus Considering Depth Information", written by Satoshi A., Sugimoto and Yoshiki Ichioka, Applied Optics, vol. 24, Nov. 14, 1985. This method is used for image signal processing in microscopes. This known technique uses a plurality of images photographed while the focal plane is being slightly shifted, detects the in-focus condition from some of the high-frequency signal components included in the images, and measures the distance to the object from this focal point position and the current condition of the lens. In addition, volume data is obtained by converting the result of the distance measurement.
U.S. Pat. No. 4,584,704 discloses the apparatus for producing three-dimensional volume data from a plurality of images which are obtained by shifting the focal point of the camera lens, this three-dimensional volume data showing a plurality of positions of the object within the field of view of the camera.